DESCRIPTION (provided by investigator): Social rejection and exclusion from social groups have been widely suggested as contributing to a broad range of societal and mental health problems, including aggression, drug abuse, suicide, and anxiety. The proposed research begins with a recognition of the pervasively social nature of adolescent and young adult human beings, a nature that includes a powerful motivation by excluding such people from social groups may therefore elicit an assortment of abnormal, antisocial, undesirable, and even pathological responses. The proposed research will employ primarily laboratory manipulations of social rejection and exclusion to investigate the direct consequences of this common but often highly aversive experience. People will be exposed by random assignment to experiences of social acceptance and social rejection, such as hearing that no other member of an ad hoc group expressed a preference to work with them individually, or a diagnostic forecast that they will be alone later in life. The first part of the application proposes to study how social exclusion causes a shift toward antisocial behaviors (including aggression) and away from prosocial behaviors (such as affiliating and helping). The second part will investigate inner psychological processes that may contribute to these behavioral manifestations. The inner processes affected by exclusion may include self-regulation and volition, emotion, and passivity. Rejection may promote depression and impair people's control over attention. The third application will pull the first two parts together to show that the impairments in self-regulation mediate the antisocial responses. The fourth part of the application will examine possible gender differences in the effects of social exclusion in terms of the basis for rejection, internalizing versus externalizing responses, and the social sphere implicated in the exclusion. The fifth project will examine social exclusion outside the laboratory, in order to elucidate how exclusion affects people in everyday life.